1. Field of the Invention
The present invention relates to a display panel driver having two large-scale integrated circuits that drive separate halves of a display panel, more particularly to a screen saving function of the display panel driver.
2. Description of the Related Art
Although the flat panel displays used in devices such as mobile telephones have conventionally been liquid crystal displays (LCDs), the technology is now shifting to organic electroluminescence (EL) displays, also known as organic light-emitting diode (OLED) displays. Organic EL displays have the advantages of high visibility and good color rendition, and can be made in large sizes. While a small organic EL display can be driven by a large-scale integrated (LSI) circuit disposed on a single semiconductor chip, for larger organic EL displays a dual scan system is used in which the display screen is divided vertically or horizontally into two halves, each driven by an LSI driver circuit on a separate chip.
A disadvantage of organic EL displays is that their display function degrades if the same image is displayed continuously. To prevent degradation, in the standby mode, the displayed image is scrolled so that it does not become ‘burned into’ the screen. The same type of screen saving function is used to protect the cathode ray tube (CRT) displays of personal computers, generally by having software continuously update the image data during standby. For devices such mobile telephones that must conserve battery power, the screen saving function is preferably implemented in the LSI driver circuits, which can operate while software execution is halted.
When the dual scan system is used, however, if the screen saving function is implemented by the two separate LSI driver circuits, two independent screen saving images are displayed simultaneously in the two halves of the screen, giving the impression that the display is not operating properly.